Many thanks to all the replies and help. There are some star performers working for NTT, kudos to them for their professionalism and brainpower. Follow-up question: We've seen great improvement by testing throughput using ChinaNetworkCommunications, AS4837. Before we switch service, does anyone have experience with their network/service/administration? Thanks, Andrew -----Original Message----- From: Andrew Staples [mailto:andrews@ltinet.net] Sent: Monday, September 08, 2008 8:33 AM To: nanog@nanog.org Subject: NTT/ChinaTelCom troubleshooting Our connectivity from the US to ChinaTelCom has been in the toilet for 2 months. The Olympics are over, and I'm assured by my Shanghai contacts that The Great Firewall of China has been relaxed, yet the problem remains. Local loops on each end test fine to other localized ip space. Symptoms include large-email delivery delays/failures, large file transfer failures. Firewalls and VPNs have been reviewed, NOCS have been contacted. Fingerpointing is raging at its finest. US endpoint is AS7358 Transit is AS2914 CN endpoint is AS4134 If there is anyone from those three networks who can help us figure out why large packets are dropping on transmits from the US to CN, I would really appreciate an off-list reply. Heck, I'll take any replies from anyone that might have some inside information or similar experiences, or give me some ideas on the best way to do some external black-hole router/mtu munging detective work on these networks. Thanks, Andrew